The invention relates to a charged particle beam system, comprising a source for emitting a beam of charged particles and a focusing device which comprises at least one coil for deflecting the beam, said at least one coil comprising a cooling member which encloses the coil and which comprises a cooling duct for transporting a cooling medium.
The invention also relates to a cooling device, a coil provided with a cooling member and a cooling member suitable for use in such a charged particle beam system.
A charged particle beam system of the kind set forth is known from U.S. Pat. No. 3,394,254.
The cited Patent Specification describes a coil for focusing an electron beam which is formed by a copper tube around which a resin-insulated wire is wound. The outer side of the coil is provided with a copper layer so that the coil fits in a cylindrical opening of a cooling member, the copper layer on the outer side of the coil engaging the inner wall of the cooling member which is also made of copper. The cooling member comprises a cooling duct which is coaxial with the coil and wherethrough water is pumped. The heat developed in the coil is first transported to the cooling duct by conduction by the copper cooling member and is subsequently discharged from the charged particle beam system via convection. In the case of a power dissipation of 30-40 W in the coil, the coil is heated to a temperature of 70.degree. C. Approximately 70% of the heat is then carried off by the cooling water.